Guido van Rossum wrote:
> On 6/30/06, Ka-Ping Yee <[EMAIL PROTECTED]> wrote:
>> On Fri, 30 Jun 2006, Andrew Koenig wrote:
>>> I hope Py3000 has lexical scoping a la Scheme...
>> Me too -- that would be really nice.
>
> That's not a very constructive proposal (especially since I don't know
> Scheme). Perhaps you could elaborate on what needs to change?
I believe the essence of their request for lexical scope boils down to
allowing rebinding. Such code like the following is legal in Scheme:
def f(x):
def incr():
x = x + 1
return x
def decr():
x = x - 1
return x
return (incr, decr)
(incr, decr) = f(1)
print incr() # 2
print incr() # 3
print decr() # 2
print decr() # 1
--
FWIW, the Scheme equivalent would be something like:
(define f (lambda (x)
(list
(lambda () (set! x (+ x 1)) x)
(lambda () (set! x (- x 1)) x))))
(let ([fs (f 1)])
(let ([incr (car fs)] [decr (cadr fs)])
(display (incr)) (newline) ; 2
(display (incr)) (newline) ; 3
(display (decr)) (newline) ; 2
(display (decr)) (newline))) ; 1
As a more personal aside, I can't imagine where I would use this in any
python program I have ever wrote. I actually never noticed that
rebinding wasn't allowed until recently.
--
Scott Dial
[EMAIL PROTECTED]
[EMAIL PROTECTED]
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